Besides endoscopes for medical and non-medical technical applications, the viewing direction of which is parallel to the longitudinal axis of the shaft of the endoscope, endoscopes having different fixed viewing directions were already developed early on. Here and in what follows, the viewing direction of an endoscope always means the direction from the distal end of the endoscope in which an object, which appears in the middle of the image acquired by means of the endoscope, lies. In many applications, however, a fixed viewing direction is disadvantageous. In the least favorable case, for example, the endoscope must be changed several times during a medical intervention. In such cases, the use of an endoscope having an in-situ adjustable or variable viewing direction is advantageous.
The observation of an object in a cavity by means of an endoscope generally requires illumination of the object. To this end, for example, an endoscope comprises light waveguides, in particular glass fibers, by means of which illumination light is transmitted from the proximal end of the endoscope along the shaft to the distal end of the endoscope. Light exit surfaces of the light waveguides at the distal end of the endoscope are arranged and formed in such a way that the entire field of view, or viewing field, is illuminated sufficiently.
In order to illuminate the entire field of view for all possible viewing directions, a plurality of light exit surfaces, through which illumination light emerges in different directions, are for example provided. At these light exit surfaces, light waveguides sometimes have curvatures with small radii immediately proximally with respect to the light exit surface. At least when changing to ever smaller shaft diameters, however, the radii of curvature are simply so small that fracture of the light waveguides is no longer the exception but the rule. When the radius of curvature is too small, furthermore, the light guiding properties of a light waveguide are lost.
DE 600 15 375 T2 describes an arrangement of a plurality of prisms. One of the prisms can be rotated about an axis in order to shine illumination light in an adjustable viewing direction. This arrangement, however, can only be miniaturized further with great outlay. For endoscopes with ever thinner shafts, alternative concepts that can be miniaturized further are necessary.